Oil leak and Coolant Flush

A mechanic just told me my 1999 3.8L V-6 is using oil.

I would like to have an idea before I take it into a repair shop; being a single female, I am subject to rip-offs. For example, my son-in-law replaced the serpentine belt in August, then in October when I had the oil changed with a coupon, the mechanic said, "This serpentine belt is the original belt and is cracked and worn, it needs to be replaced, " then handed me a quote for abt $300. I have not been back to that shop!

3100 miles ago, I had the oil changed and then drove abt 8 hour to Charlotte, NC. While there, a friend told me that there was an "oil spot" on the driveway when I left her house. I checked, and it was a quart low, after having just been serviced. The next day, I looked where I had parked, but could see no spot or leakage. I don't think it should have used a quart of oil that soon.

I have the oil changed every 3000 miles. I have the 1999-2004 Haynes Repair Manual, and have read Ch 1-11 on oil changes, and page 0-21, section 44 on Oil Leaks. Since I don't know how to "degrease the transmission, " I put an unfolded cardboard box under the engine.

Where should I look for a possible leak spot, in relation to the front grill? Such as top right or bottom left corner or center? Also, what happens if I use a different weight oil than specified? Is there a big difference bet. SAE 30 and SAE 5w 30?

In addition, I need the coolant system flushed. Again, I have read the manual and it suggests using a chemical cleaner. I have prices from $80 - $120 for this service, using a pumping system. Do these prices fall in a normal range? While it sounds as if I can do this myself with the kit from Auto Zone, does the "pump" work better than my garden hose would?

Thanks, Tina